U.S. Market fences are ALL long, extending all the way to the back of the table saw?s table, some even locking back there as well as in front. Euro fences tend to be short - just long enough to extend a little past the back of the saw blade when the blade is at maximum height. Some can be shortened for shallower cuts.
When you think about it, beyond the back of the exposed blade PLUS the distance to the riving knife, which keeps the kerf open, there really isn?t any need to keep the stock behind the blade against the fence. In fact, if the piece being ripped Wish Bones (I.e. Opens up like a ?Y? ) it can push against the fence behind the cut and try to move the whole piece of stock being ripped AWAY from the fence and bind against the blade. In an extreme case, it could push the riving knive out of alignment with the blade enough to allow the stock to contact the blade?s rear teeth - the ones that typcially initiate a ?kickback?. OR
- it could try and push the end of the fence away from the blade - also not a ?good thing?.
Now let us examine The Short Fence vs The Long Fence from a leverage perspective. And let?s begin with both fences locked down only at the front of the table. If you apply one pound of force to the end of a one foot lever you produce one foot pound of torque. Apply the same one pound of force to the end of a two foot lever and you produce TWO foot pounds of torque - twice that of the one foot lever. Now if you?re tying to lift something, the longer the lever arm the better. BUT - if you?re trying to keep the lever from moving, which is what you want to do if the lever is your rip fence, LONGER ain?t better at all, SHORTER IS BETTER. Kind of obvious when you think about it - right?
OK - so what if we can lock down BOTH the front AND rear of the fence? Well if you look at it from a Moment Diagram perspective - forces applied to lever arms, The Short Fence vs The Long Fence Locked Down At Both Ends is about a push - basically they?d work the same.
BUT - what?s it take to lock down both the front and rear of the fence AND keep it parallel to the blade its entire length? If the back locks down before the front, or the front locks down before the back, you could cause the fence to go out of parallel with the blade. If the front of the fence is closer to the line of the blade you?ll bind the stock against the outside of the saw blade. If the front is farther from the line of the blade you?ll bind the stock against the inside of the blade. Neither situation is desirable.
ALL the mechanisms to lock the front and rear of the fence down together and parallel to the saw blade introduce one more critical set up requirement - AND one more thing that needs to be checked periodically and adjusted if necessary. Don?t know about you, but I?d rather spend time cutting wood rather than checking and adjusting things BEFORE I can cut wood.
I can only think of one reason for a longer fence - a place to attach Hold Downs behind the cut - Board Buddies, magnetic Draw-Tite etc. - all keep the stock down on the saw table and some also pull the stock into the fence. You don?t want the stock behind the blade coming up off the table - and perhaps into those spinning teeth rising up out of the table top. It?s those rear teeth that raise all the hell. ANYTHING that can cause the stock to come in contact with those rear teeth is ?not good?. The Rear Teeth ARE BAD!
So other than the fact that you're use to a long fence is there any reason why you wouldn't even consider going with a short fence?
charlie b